Sowing distrust has turned tide in PSNI's favour
The senior police officer borrowed a phrase from the past. "They only have to get lucky once," he said.
And "lucky" in the context of violent dissident republican activity could have "catastrophic" consequences he warned.
He knows the various factions are reeling from the recent intelligence successes.
"They are looking at each other as much as us now," he said.
And creating "uncertainty and a lack of trust within" is all part of a complex and covert intelligence battle.
Staying one step ahead of the dissident plans and plots is a day-to-day task. And rarely do we get a glimpse of those secret and hidden plays.
It means watching, listening, recording and also having eyes and ears among those different groups – the IRA coalition, Oglaigh na hEireann and the Continuity IRA.
And the more they are stopped in their tracks, so the more they look at each other.
This is what is meant by "creating uncertainty".
And the more they have to worry about who is in their rooms and conversations, so the more they have to think before moving. They can become glued to the spot.
When the dissident IRA coalition of the Real IRA, Republican Action Against Drugs and a number of unaffiliated dissidents was pulled together it was about tightening internal security.
But the eyes and ears – sometimes electronic, other times human – watching and listening for MI5 and police intelligence are still on the inside.
"The trick is keeping every tool available to you," that senior police source said.
But it's not just about having information.
"It's only the starter," he continued. "The real trick is turning intelligence into evidence."
And we can see in the training camp operation how long these things are left to soak, how surveillance of one individual brings others into the frame.
The longer MI5 and the police can wait, the more they learn. So, for those in intelligence, it is about getting close enough to the dissidents to see and hear and being just far enough away that they don't know they are being watched and recorded.
But it is not just about the technical side of intelligence.
It is also about the information that comes from the inside, from Covert Human Intelligence Sources (CHIS).
They are paid for what they know and what they tell from within that circle of dissident planning.
If they are found out, they are dead.
And this is all part of the danger and the task of intelligence.
You have to be that close, without being too close and too obvious.
And it is why the dissidents "are looking at each other", knowing that they are being compromised not just through those tools available to the security service and police intelligence, but by some of those who sit among them.
The recent funeral of the senior dissident Tony Catney was intended to send out a message of confidence and strength.
Big numbers, masked men as a guard of honour, a volley of shots fired and those pictures released to be seen.
But the real test for those different dissident groups is getting bombs to explode and targets into their firing range.
Intelligence is about stopping that, and it is working. But there is no room for complacency, and this is why we have heard that warning again that "they only have to get lucky once".
What happened in the attacks in which police constable Ronan Kerr, prison officer David Black, and sappers Mark Quinsey and Patrick Azimkar were killed is still fresh in the memory.
There is not always intelligence and, in a recent interview with this paper, Chief Constable George Hamilton highlighted an ongoing and severe threat.